Waterhammer modelling of viscoelastic pipes with a time-dependent Poisson's ratio

Keramat, Alireza; Kolahi, Arash Ghaffarian; Ahmadi, Ahmad

doi:10.1016/j.jfluidstructs.2013.08.013

Cited by 44 publications

(14 citation statements)

References 33 publications

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“…Proper modelling of flows of liquids under pressure in such systems remains a significant challenge. Among the key issues widely discussed in new publications on the subject, special emphasis is placed on the correct modelling: of the time-varying hydraulic resistance (Vardy and Brown, 2003;Zarzycki et al, 2011;Reddy et al, 2012), cavitation (Zarzycki and Urbanowicz, 2006;Lewandowski, 2009, 2012;Bergant et al, 2006;Karadžić et al, 2014;Soares et al, 2015), the interaction between the liquid and walls of the conduit Henclik, 2015;Zanganeh et al, 2015), the viscoelastic phenomenon that occurs during the flow in a piping made of engineering polymers (Weinerowska-Bords, 2015; Soares et al, 2012; Keramat et al, 2013;Pezzinga et al, 2014;Urbanowicz et al, 2016). Taking into account all of the above phenomena while simulating unsteady flows has seemed impossible until recently.…”

Section: Introductionmentioning

confidence: 99%

Analytical expressions for effective weighting functions used during simulations of water hammer

Urbanowicz

2017

jtam

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For some time, work has been underway aimed at significant simplification of the modelling of hydraulic resistance occurring in the water hammer while maintaining an acceptable error. This type of resistance is modelled using a convolution integral, among others, from local acceleration of a liquid and a certain weighting function. The recently completed work shows that during efficient calculations of the convolution integral, the effective weighting function used does not have to be characterised by large convergence with a classical function (according to Zielke during laminar flow and to Vardy-Brown during turbulent flow). However, it must be a sum of at least two or three exponential expressions so that the final results of the simulation could be considered as satisfactory. In this work, it has been decided to present certain analytical formulas using which it will be possible to determine the coefficients of simplified effective weighting functions in a simple direct way.

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Section: Introductionmentioning

confidence: 99%

Analytical expressions for effective weighting functions used during simulations of water hammer

Urbanowicz

2017

jtam

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“…However, for the time-domain water-hammer solution where several parameters may be incorporated in the model, an analytical solution for the CRLB cannot be derived, and a numerical approach is needed. Computational approaches allow for the application of a versatile transient solver that includes advanced models of viscoelasticity, turbulence, fluid-structure interaction, and non-Newtonian fluids, among others, with various types of boundary conditions (Covas et al 2005;Ahmadi and Keramat 2010;Keramat et al , 2013Meniconi et al 2014;Majd et al 2016;Meniconi et al 2017;Ferreira et al 2018). In this view, any arbitrary valve type and consequently valve maneuver with any nonlinear closure pattern or pipe system equipment such as pumps or pressure suppression devices can be adopted in such numerical formulation.…”

Section: Numerical Formulation Of Crlbmentioning

confidence: 99%

Cramer-Rao Lower Bound for Performance Analysis of Leak Detection

et al. 2019

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Due to random noise in real measurements, leak detection (estimation of leak size and location) is subject to a degree of uncertainty. This paper provides a framework to investigate the lower bound of the variance of a leak's variable estimation and delineates the parameters upon which this lower bound depend. This is accomplished by applying the Cramer-Rao lower bound (CRLB) principle to the leak detection problem. For a given data set, CRLB gives the minimum mean square error of any unbiased estimator. The CRLB is evaluated using the Fisher information, which is evaluated from direct differentiation of the water-hammer characteristics equations. The results show that the CRLB of the leak-size estimate increases with time of closure and noise level but reduces with the duration of the measured signal. It is also shown that the CRLB is instrumental in the systematic design of efficient transient tests for leak detection. The error of leak-size estimates rises remarkably with setting distances between consecutive potential leaks of less than half the minimum wavelength of the probing signal. More conclusions are drawn on appropriate mesh-size for inverse transient analysis (ITA), maximum possible accuracy in successful localization, and its probability subject to the physical situation's parameters.

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“…With respect to elastic materials, when a circumferential stress, σ, is applied to a viscoelastic material, the total strain, , is given by the sum of the instantaneous elastic, el , and retarded component, r [35][36][37][38][39][40][41][42]…”

Section: Appendix a Single Element Kelvin-voigt (1 K-v) Modelsmentioning

confidence: 99%

On the Role of Minor Branches, Energy Dissipation, and Small Defects in the Transient Response of Transmission Mains

Meniconi

Brunone

Frisinghelli³

2018

Water

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Abstract:In the last decades several reliable technologies have been proposed for fault detection in water distribution networks (DNs), whereas there are some limitations for transmission mains (TMs). For TM inspection, the most common fault detection technologies are of inline types-with sensors inserted into the pipelines-and then more expensive with respect to those used in DNs. An alternative to in-line sensors is given by transient test-based techniques (TTBTs), where pressure waves are injected in pipes "to explore" them. On the basis of the results of some tests, this paper analyses the relevance of the system configuration, energy dissipation phenomena, and pipe material characteristics in the transient behavior of a real TM. With this aim, a numerical model has been progressively refined not only in terms of the governing equations but also by including a more and more realistic representation of the system layout and taking into account the actual functioning conditions. As a result, the unexpected role of the minor branches-i.e., pipes with a length smaller than the 1% of the length of the main pipe-is pointed out and a preliminary criterion for the system skeletonization is offered. Moreover, the importance of both unsteady friction and viscoelasticity is evaluated as well as the remarkable effects of small defects is highlighted.

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Waterhammer modelling of viscoelastic pipes with a time-dependent Poisson's ratio

Cited by 44 publications

References 33 publications

Analytical expressions for effective weighting functions used during simulations of water hammer

Analytical expressions for effective weighting functions used during simulations of water hammer

Cramer-Rao Lower Bound for Performance Analysis of Leak Detection

On the Role of Minor Branches, Energy Dissipation, and Small Defects in the Transient Response of Transmission Mains

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